➜ ranch_proxy_protocol git:(master) rebar3 compile
===> Verifying dependencies...
===> Fetching ranch v1.6.2
===> Analyzing applications...
===> Compiling ranch
_build/default/lib/ranch/src/ranch_ssl.erl:141:7: Warning: ssl:ssl_accept/3 is removed; use ssl_handshake/1,2,3 instead
===> Analyzing applications...
===> Compiling ranch_proxy_protocol
===> Compiling src/ranch_proxy_protocol.erl failed
src/ranch_proxy_protocol.erl:443:14: variable '_ClientCert' is already bound. If you mean to ignore this value, use '_' or a different underscore-prefixed name